Bone cement is used e.g. in connection with surgical replacement of a hip joint. Bone cement generally consists of akrylate plastic, which is biocompatible. Depending on the use, bone cement has got different viscosity characteristics. For use in connection with hip joint replacements, the viscosity is often quite high, whereas the bone cement used for e.g. spinal disc enhancements has lower viscosity. This invention mainly relates to mixing and application of bone cements with higher viscosity, but is just as useful for low viscosity applications.
For simplicity, the term bone cement will be used throughout this application, although the invention can be used for any other kind of paste that requires mixing prior to application.
Presently, mixing of bone cement ingredients is mostly done in a separate vessel, whereupon the mixed bone cement is put into a bone cement applicator that generally is made of stainless steel. This method has some severe drawbacks:                1. Mixing of the bone cement should preferably be performed under vacuum, since low ambient pressure reduces the presence of gas impurities in the bone cement, that leads to a connection with reduced strength. The vacuum treatment is often performed after the components of the bone cement have been mixed. Applying the prior art method, the mixed (and vacuum treated) bone cement must be put into an applicator, which increases the risk of adding gas impurities to the bone cement.        2. The applicator is usually not of single use type, which makes it necessary to disassemble the applicator to be able to clean it and sterilize it properly after it has been used. Additionally, the applicator wears down by time.        
The object of this invention is to provide a single use mixer/applicator in which the bone cement is mixed under vacuum and that is capable of handling bone cement with high viscosity.